Download Organization of the antero

Organization of the
antero-lateral abdominal
wall
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Anterolateral Abdominal Wall
• Although the abdominal wall is continuous, it is subdivided into the
anterior wall, right and left lateral walls (flanks), and posterior
wall for descriptive purposes.
• Layers of anterior abdominal wall
• Skin
• Subcutaneous (Superficial fascia): Fatty and membranous
• Deep fascia
• Muscles and their aponeurosis:
• Extra peritoneal tissue
• Peritoneum.
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Skin
• The skin attaches loosely to the subcutaneous tissue, except
at the umbilicus, where it adheres firmly.
• Shows ‘creases' which represent the lines of orientation of
collagen fibres in the dermis- Langer's lines.
• These lines are surgically important – incisions along them
heal better leaving a thin scar; while those across them
leave big scars.
• In pregnant women, obese people and those with
abdominal distention from whatever cause, there are dark
elongate lines called striae gravidara.
• The skin is very sensitive to touch, and quickly when
touched, the muscles contract.
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Fascia of the Anterolateral
Abdominal Wall
• Consists of two layers;
• Superficial fatty layer (Camper's fascia) containing
variable amounts of fat, more in females and in the
lower abdomen.
• Deep membranous layer (Scarpa's fascia).
(+) Contains fibrous tissue and very little fat.
(+) Fuses with fascia lata below inguinal ligament)
(+) Continuous with the superficial perineal fascia
(Colle's fascia) and with that investing the scrotum
and penis. Note: Deep fascia is Unremarkable
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Applied anatomy
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There are 4 main muscles to note:
• External
oblique;
Internal
oblique;
Transversus abdominis; Rectus abdominis
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Transverse Internal surfaces of 7
abdominal and 12th costal
cartilages,
thoracolumbar fascia,
iliac crest, and lateral
third of inguinal
ligament
Linea alba with
aponeurosis of
internal oblique,
pubic crest, and
pecten pubis via
conjoint tendon
Internal
oblique
Thoracolumbar fascia,
anterior two-thirds of
iliac crest, and lateral
half of inguinal
ligament
Inferior borders of
10 and 12th ribs,
linea alba, and
pecten pubis via
conjoint tendon
External
oblique
External surfaces of 5
and 12th ribs
Linea and alba,
pubic tubercle, and
anterior half of iliac
crest
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Thoracoabdominal Compresses
nerves (anterior and supports
rami of inferior 6 abdominal
thoracic nerves) viscera
and first lumbar
nerves
Transverse
abdominal
Compress and Internal
support
oblique
abdominal
viscera, flex
and rotate
trunk
Thoracoabdominal
nerves (inferior 5
[T7 and T11]
thoracic nerves)
and subcostal
nerve
External
oblique
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The Rectus Sheath
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Rectus sheath
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Location
• Fibrous compartment for rectus abdominis muscle in the
paramedian abdominal wall.
• Formation
• Formed of the aponeurosis of abdominal muscles.
• It
has
a
posterior
layer
and
anterior
layer.
Proximal 1/3rd
• The anterior layer joins the aponeurosis of the external oblique
to form the anterior wall of the rectus sheath.
• The posterior layer joins with the aponeurosis of the transversus
abdominis to form the posterior wall of the rectus sheath.
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Location…
• Middle 1/3 rd
• Aponeurosis of internal oblique joins external oblique
aponeurosis to form anterior wall.
• Posterior wall is formed by aponeurosis of transversus
abdominis muscle
• Distal 1/3 rd
• Mid way between umbilicus and pubic crest all three
aponeurosis form the anterior layer
• The posterior layer is formed only by fascia transversalis
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Location…
• The anterior and posterior layers fuse in the midline to form
the linear alba, a fibrous intersection extending from the
xiphoid process to the pubic symphysis.
• The inferior ¼ of the rectus sheath is deficient posteriorly. The
limit of the posterior wall is marked by the arcuate line
• The lateral margin of rectus sheath is called linea semilunaris
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Contents of Rectus Sheath
• Rectus abdominis muscle
• Inferior and superior epigastric vessels
• Terminal parts of the lower five intercostal
nerves, and the Subcostal nerve.
• Fibro fatty connective tissue
• Occasionally lymph node(s)
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Extra peritoneal fascia
• Transparent ‘membrane' which lines the inside
of the abdominal wall.
• Its parts are named according to what it lines
e.g.
(+) diaphragmatic fascia;
(+) iliac fascia;
(+) psoas fascia.
(+) fascia transversalis ( part covering the
muscle transversus abdominis ).
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Blood supply to the anterior abdominal
wall
• Arteries
• Inferior epigastric : External iliac
• Superficial circumflex iliac :
Femoral arterty
• Deep circumflex iliac : femoral
artery
• Superior epigastric : internal
thoracic
• Lower intercostal : Abdominal
Aorta
• Subcostal arteries : Abdominal
aorta
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Veins
• The veins correspond to the arteries,
• but: Inferior epigastric vein anastomoses with lateral thoracic
vein.
• Superficial epigastric vein anastomoses with lateral thoracic
vein.
• These two unite the veins of the upper and lower halves of the
body (of the azygous system).
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Lymphatic Drainage
• Superior to the umbilical
level:
• Axillary nodes
• Parasternal nodes
• Inferior to the umbilical
level:
• Superficial Inguinal
lymph nodes
• Deep inguinal nodes
• External iliac nodes
• Lumbar nodes
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Innervation
• The skin and muscles of the anterolateral abdominal wall are
supplied mainly by the following nerves
• Thoracoabdominal nerves: the distal, the anterior rami of the
inferior six thoracic spinal nerves; Lateral (thoracic) cutaneous
branches: of the thoracic spinal nerves T7 and T9 or T10.
• Subcostal nerve: the large anterior ramus of spinal nerve T12.
• Iliohypogastric and ilioinguinal nerves: terminal branches of the
anterior ramus of spinal nerve L1.
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The internal surface of anterior
abdominal wall
• Inferior to the umbilicus, there are 5 folds:
• The median umbilical fold is due to median umbilical ligament,
the remnant of the urachus, which develops from the allantois. It
attaches to the urinary bladder.
• 2 medial umbilical folds formed by medial umbilical ligaments
– the obliterated umbilical arteries.
• 2 lateral umbilical folds – formed by the inferior epigastric
vessels
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INGUINAL REGION
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The inguinal canal
• Canal represents path taken by testis out of the abdomen.
• Boundaries
• Floor:
Inguinal
ligament
and
lacunar
ligament
Roof: Arching fibres of internal oblique and transversus
abdominis.
• Antero lateral:Aponeurosis of external oblique
• Posterior: Fascia transversalis laterally and conjoint tendon
medially (of transversus and internal oblique abdominal muscles)
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Applied anatomy
Direct hernia
•
•
•
•
•
•
Less common type
more likely in older men (over 40).
Protrudes anteriorly through the posterior wall of inguinal canal
Medial to inferior epigastric artery.
passes through inferior part of inguinal triangle.
Does not pass through the deep inguinal ring, but pass through
superficial ring.
• Usually results from weakening of the Conjoint tendon
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Indirect hernia
•
•
•
•
•
•
More common type, makes 75% of all.
more common in male children,
Takes the path taken by testis through inguinal canal
Leaves lateral to inferior epigastric artery.
Passes outside inguinal triangle.
Passes through the deep inguinal ring and superficial ring to enter
the scrotum
• More likely in patent processus vaginalis
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Review Questions
• Describe the muscles, blood supply, lymphatic
drainage and sensory innervation of the anterior
abdominal wall
• Discuss the formation and contents of the inguinal
canal. Add notes on the distinction between direct
and indirect inguinal hernias. List six structures
that must be safeguarded during hernial repair
• Describe the formation and contents of the rectus
sheath
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Review Questions
• Outline the general organization of the superficial
fascia of the anterior abdominal wall, and the
perineum. Add clinical notes on the implication of
this organization
• Describe in detail the pattern and clinical
significance of the blood supply of the anterior
abdominal wall.
• State the advantages and disadvantages of the
various incisions in the anterior abdominal wall.
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